Update _mongoClientPromise type error (#46985)

Fixes #46983. The type of `_mongoClientPromise` has been added as
Promise<MongoClient> which fixes the error.
… file @/examples/with-mongodb/lib/mongodb.ts

![image](https://user-images.githubusercontent.com/96732471/224264097-2f4f3181-73b3-4ebd-b756-2301bab1a3fd.png)


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Co-authored-by: JJ Kasper <jj@jjsweb.site>

examples/with-mongodb/lib/mongodb.ts

@@ -13,11 +13,15 @@ let clientPromise: Promise<MongoClient>
 if (process.env.NODE_ENV === 'development') {
   // In development mode, use a global variable so that the value
   // is preserved across module reloads caused by HMR (Hot Module Replacement).
-  if (!global._mongoClientPromise) {
-    client = new MongoClient(uri, options)
-    global._mongoClientPromise = client.connect()
+  let globalWithMongo = global as typeof globalThis & {
+    _mongoClientPromise?: Promise<MongoClient>
   }
-  clientPromise = global._mongoClientPromise
+
+  if (!globalWithMongo._mongoClientPromise) {
+    client = new MongoClient(uri, options)
+    globalWithMongo._mongoClientPromise = client.connect()
+  }
+  clientPromise = globalWithMongo._mongoClientPromise
 } else {
   // In production mode, it's best to not use a global variable.
   client = new MongoClient(uri, options)